Arrow: Use case instead of wrapping a map/list

Wrapping the list seems to introduce an odd behavior where
`null` values are converted to an empty list `[]`.

Resolves #251

Author: Fokko

dev/provision.py

@@ -339,3 +339,23 @@
 )
 
 spark.sql("INSERT INTO default.test_table_add_column VALUES ('2', '2')")
+
+spark.sql(
+    """
+CREATE TABLE default.test_table_empty_list_and_map (
+    col_list array<int>,
+    col_map map<int, int>
+)
+USING iceberg
+TBLPROPERTIES (
+    'format-version'='1'
+);
+"""
+)
+
+spark.sql(
+    """
+INSERT INTO default.test_table_empty_list_and_map
+VALUES (null, null)
+"""
+)

pyiceberg/io/pyarrow.py

@@ -1052,24 +1052,12 @@ def field(self, field: NestedField, _: Optional[pa.Array], field_array: Optional
         return field_array
 
     def list(self, list_type: ListType, list_array: Optional[pa.Array], value_array: Optional[pa.Array]) -> Optional[pa.Array]:
-        return (
-            pa.ListArray.from_arrays(list_array.offsets, self.cast_if_needed(list_type.element_field, value_array))
-            if isinstance(list_array, pa.ListArray)
-            else None
-        )
+        return list_array.cast(schema_to_pyarrow(list_type)) if isinstance(list_array, pa.ListArray) else None
 
     def map(
         self, map_type: MapType, map_array: Optional[pa.Array], key_result: Optional[pa.Array], value_result: Optional[pa.Array]
     ) -> Optional[pa.Array]:
-        return (
-            pa.MapArray.from_arrays(
-                map_array.offsets,
-                self.cast_if_needed(map_type.key_field, key_result),
-                self.cast_if_needed(map_type.value_field, value_result),
-            )
-            if isinstance(map_array, pa.MapArray)
-            else None
-        )
+        return map_array.cast(schema_to_pyarrow(map_type)) if isinstance(map_array, pa.MapArray) else None
 
     def primitive(self, _: PrimitiveType, array: Optional[pa.Array]) -> Optional[pa.Array]:
         return array

tests/test_integration.py

@@ -93,6 +93,11 @@ def table_test_table_sanitized_character(catalog: Catalog) -> Table:
     return catalog.load_table("default.test_table_sanitized_character")
 
 
+@pytest.fixture()
+def table_test_empty_list_and_map(catalog: Catalog) -> Table:
+    return catalog.load_table("default.test_table_empty_list_and_map")
+
+
 TABLE_NAME = ("default", "t1")
 
 
@@ -417,8 +422,15 @@ def test_upgrade_table_version(table_test_table_version: Table) -> None:
 
 
 @pytest.mark.integration
-def test_reproduce_issue(table_test_table_sanitized_character: Table) -> None:
+def test_sanitize_column_names(table_test_table_sanitized_character: Table) -> None:
     arrow_table = table_test_table_sanitized_character.scan().to_arrow()
     assert len(arrow_table.schema.names), 1
     assert len(table_test_table_sanitized_character.schema().fields), 1
     assert arrow_table.schema.names[0] == table_test_table_sanitized_character.schema().fields[0].name
+
+
+@pytest.mark.integration
+def test_null_list_and_map(table_test_empty_list_and_map: Table) -> None:
+    arrow_table = table_test_empty_list_and_map.scan().to_arrow()
+    assert arrow_table["col_list"].to_pylist() == [None]
+    assert arrow_table["col_map"].to_pylist() == [None]